// make color blacker, $amount=1 => black, $amount=0 => original color 
@function toblack($color, $amount) {
	@return mix(black, $color, $amount*100%);
	//@return hsl(hue($color), saturation($color), lightness($color) * (1 - $amount));
}

// make color whiter, $amount=1 => white, $amount=0 => original color 
@function towhite($color, $amount) {
	@return mix(white, $color, $amount*100%);
	//@return hsl(hue($color), saturation($color), 100%*$amount + (1-$amount)*lightness($color));
}

// return transparent black rgba code
@function tr($opacity) {
	@return rgba(0,0,0,$opacity);
};